Recently, along with the explosive increase of the amount of information and data handled by companies and government offices, the amount of processed data or the capacity of stored data in large-scale computers such as host computers, servers, and storage subsystems coupled to the host computers have also increased significantly. Especially, unlike the severs or other information processing systems, storage subsystems are devices specialized in storing data, which utilize a large number of HDDs (Hard Disk Drives) as data storage media having large capacity and high reliability, which are managed and operated via a RAID (Redundant Array of Independent (Inexpensive) Disks) configuration.
Patent Literature 1 discloses an art related to the RAID system. Patent Literature 1 discloses dividing a logical volume composed of RAID groups formed of the same type of storage drives (hereinafter referred to as drives) into pools, and managing the same. It is a common technical knowledge that a RAID group is composed of the same type of drives, as taught in Patent Literature 1.